1. Field of the Invention.
This invention relates in general to a network device, and in particular, to a network repeater having automatic speed switching capability.
2. Description of Related Art.
Recent advancements in the art of data communications have provided great strides in resource sharing amongst computer systems through the use of networks which offer reliable high-speed data channels. Networks allow versatility by defining a common standard for communication so that information independent of vendor equipment may be exchanged across user applications. As the popularity of networks increase so does the demand for performance. More sophisticated protocols are being established to meet this demand and are utilizing existing twisted pair wires in office buildings so that virtually all computer literate users have access to resources with minimal expense.
As will be appreciated by those skilled in the art, communication networks and their operations can be described according to the Open Systems Interconnection (OSI) model which includes seven layers including an application, presentation, session, transport, network, link, and physical layer. The OSI model was developed by the International Organization for Standardization (ISO) and is described in xe2x80x9cThe Basics Book of OSI and Network Managementxe2x80x9d by Motorola Codex from Addison-Wesley Publishing Company, Inc., 1993 (First Printing September 1992).
Each layer of the OSI model performs a specific data communications task, a service to and for the layer that precedes it (e.g., the network layer provides a service for the transport layer). The process can be likened to placing a letter in a series of envelopes before it is sent through the postal system. Each succeeding envelope adds another layer of processing or overhead information necessary to process the transaction. Together, all the envelopes help make sure the letter gets to the right address and that the message received is identical to the message sent. Once the entire package is received at its destination, the envelopes are opened one by one until the letter itself emerges exactly as written.
In a data communication transaction, however, each end user is unaware of the envelopes, which perform their functions transparently. For example, an automatic bank teller transaction can be tracked through the multilayer OSI system. One multiple layer system (Open System A) provides an application layer that is an interface to a person attempting a transaction, while the other multiple layer system (Open System B) provides an application layer that interfaces with applications software in a bank""s host computer. The corresponding layers in Open Systems A and B are called peer layers and communicate through peer protocols. These peer protocols provide communication support for a users application, performing transaction related tasks such as debiting an account, dispensing currency, or crediting an account.
Actual data flow between the two open systems (Open System A and Open System B), however, is from top to bottom in one open system (Open System A, the source), across the communications line, and then from bottom to top in the other open system (Open System B, the destination). Each time that user application data passes downward from one layer to the next layer in the same system more processing information is added. When that information is removed and processed by the peer layer in the other system, it causes various tasks (error correction, flow control, etc.) to be performed.
The ISO has specifically defined all seven layers, which are summarized below in the order in which the data actually flows as they leave the source:
Layer 7, the application layer, provides for a user application (such as getting money from an automatic bank teller machine) to interface with the OSI application layer. That OSI application layer has a corresponding peer layer in the other open system, the bank""s host computer.
Layer 6, the presentation layer, makes sure the user information (a request for $50 in cash to be debited from your checking account) is in a format (i.e., syntax or sequence of ones and zeros) the destination open system can understand.
Layer 5, the session layer, provides synchronization control of data between the open systems (i.e., makes sure the bit configurations that pass through layer 5 at the source are the same as those that pass through layer 5 at the destination).
Layer 4, the transport layer, ensures that an end-to-end connection has been established between the two open systems and is often reliable (i.e., layer 4 at the destination confirms the request for a connection, so to speak, that it has received from layer 4 at the source).
Layer 3, the network layer, provides routing and relaying of data through the network (among other things, at layer 3 on the outbound side an address gets slapped on the envelope which is then read by layer 3 at the destination).
Layer 2, the data link layer, includes flow control of data as messages pass down through this layer in one open system and up through the peer layer in the other open system.
Layer 1, the physical interface layer, includes the ways in which data communications equipment is connected mechanically and electrically, and the means by which the data moves across those physical connections from layer 1 at the source to layer 1 at the destination.
The primary standard for Local and Metropolitan Area Network technologies is governed by IEEE Std. 802. IEEE Std. 802 describes the relationship among the family of 802 standards and their relationship to the ISO OSI Basic Reference Model. Generally, IEEE Std. 802 prescribes the functional, electrical and mechanical protocols, and the physical and data link layers for Local and Metropolitan Area Networks (LAN/MAN) The specification augments network principles, conforming to the ISO seven-layer model for OSI, commonly referred to as xe2x80x9cEthernetxe2x80x9d. In the hierarchy of the seven-layer model, the lowest layers, the so-called physical and data link layers, comprise functional modules that specify the physical transmission media and the way network nodes interface to it, the mechanics of transmitting information over the media in an error-free manner, and the format the information must take in order to be transmitted.
While there are several LAN technologies in use today, Ethernet is by far the most popular. The definitions of an Ethernet Repeater functions are contained in the IEEE 802.3 specification, which is herein incorporated by reference. This standard defines attributes which can be used by a management function within an IEEE 802.3 Ethernet Repeater to monitor network behavior.
The vast majority of computer vendors today equip their products with 10 Mbps Ethernet attachments, making it possible to link all manner of computers with an Ethernet LAN. Nevertheless, the need for faster data transmission has led to the development of Fast Ethernet standards which carry Ethernet frames at 100 Mbps. When the IEEE standardization committee began work on a faster Ethernet system, two approaches were presented. One approach was to speed up the original Ethernet system to 100-Mbps, keeping the original CSMA/CD medium access control mechanism. This approach is called 100BASE-T Fast Ethernet.
Another approach presented to the committee was to create an entirely new medium access control mechanism, one based on hubs that controlled access to the medium using a xe2x80x9cdemand priorityxe2x80x9d mechanism. This new access control system transports standard Ethernet frames, but it does it with a new medium access control mechanism. This system was further extended to allow it to transport token ring frames as well. As a result, this approach is now called 100VG-AnyLAN.
The IEEE decided to create standards for both approaches. The 100BASE-T Fast Ethernet standard described here is part of the original 802.3 standard, which was incorporated by reference earlier. The 100VG-AnyLAN system is standardized under a new number: IEEE 802.12, herein incorporated by reference.
The Fast Ethernet standards both include mechanisms for Auto-Negotiation of the media speed. As the 100 Mbps standard becomes more widely adopted, computers are being equipped with an Ethernet interface that operates at both 10 Mbps and 100 Mbps. The Auto-Negotiation function is an optional part of the Ethernet standard that makes it possible for devices to exchange information about their abilities over a link segment. This, in turn, allows the devices to perform automatic configuration to achieve the best possible mode of operation over a link. At a minimum, Auto-Negotiation can provide automatic speed matching for multi-speed devices at each end of a link. Multi-speed Ethernet interfaces can then take advantage of the highest speed offered by a multi-speed hub port.
The Auto-Negotiation protocol includes automatic sensing for other capabilities as well. For example, a switched hub that is capable of supporting full duplex operation on some or all of its ports can advertise that fact with the Auto-Negotiation protocol. Interfaces connected to the switch hub port that also support full duplex operation can then configure themselves to use the full duplex mode in interaction with the hub.
Integrated multi-port repeaters exist which provide separately either 10 Mb/s or 100 Mb/s functionality. However, the incorporation of 10 Mb/s or 100 Mb/s repeater functionality within a single repeater is beyond the scope of IEEE 802.3 standard.
FIG. 9 illustrates the traditional solution 900 of providing 100 Mbps functionality in a network system along with 10 Mbps functionality. A 10 Mbps repeater 910 is connected to a 100 Mbps repeater 912 through a bridge 914. Ten Mbps devices 916 are connected to the 10 Mbps repeater 910. One hundred Mbps devices 918 are connected to the 100 Mbps repeater. Upgrading a device to Fast Ethernet requires disconnecting the device 916 from the 10 Mbps repeater 910 and re-routing cable from the device 916 to the 100 Mbps repeater 914. However, this procedure is time consuming and confusing. Furthermore, to provide the dual speed functionality, both types of repeaters and a bridge must be purchased. Thus, the traditional solution is too expensive.
If a 10 Mbps segment is replaced with a 100 Mbps segment, fast link pulses (FLPs) will be received by the repeater hub, and the Auto-Negotiation protocol will result in the hub port operating at 100-Mbps as long as all interfaces connected to the repeater hub can operate at 100-Mbps. The change from 10-Mbps to 100-Mbps will occur with no manual intervention.
Auto-Negotiation ensures that all devices attached to the hub are operating at the highest common denominator. Since a repeater hub is used to create a shared signal channel for all devices attached to the repeater ports, that shared signal channel must operate no faster than the slowest device attached to it.
If an repeater hub has one of its ports attached to a device that only supports 10 Mbps transmissions while the rest of the ports are attached to 100 Mbps devices, the hub will negotiate a speed of 10-Mbps for all ports, since that is the highest common denominator for all repeated ports. When every device attached to the repeater hub is capable of operating at 100-Mbps, then the hub will negotiate 100-Mbps for all ports.
If there is no common technology detected at either end of the link, then the Auto-Negotiation protocol will not make a connection, and the port will be left in the off condition.
It can therefore be seen that there is a need for a repeater which provides both 10 Mb/s or 100 Mb/s functionality.
It can also be seen that there is a need for a repeater which automatically switches to either a 10 Mb/s backplane/segment or a 100 Mb/s backplane/segment.
To overcome the limitations in the prior art described above, and to overcome other limitations that will become apparent upon reading and understanding the present specification, the present invention discloses a network repeater having automatic speed switching capability.
The present invention solves the above-described problems by providing a first repeater logic means for connecting devices operating at the first rate to a first backplane, a second repeater logic means for connecting devices operating at a second rate to a second backplane, and a port switching fabric, coupled to the first and second repeater logic means, for determining the transmission rate of a signal at a port and routing the signal to one of the repeater logic according to the transmission rate determination.
One aspect of the present invention is that the repeater includes an integrated serial controller for accessing internal management counters, control and status information.
Another aspect of the present invention is that the repeater includes LEDs for providing status information about the repeater.
Yet another aspect of the present invention is that the repeater includes a media access controller for controlling functions including the transmission, loopback and reception of Ethernet frames.
Another aspect of the present invention is that the repeater includes a direct memory access controller for servicing the media access controller and controlling memory.
Still another aspect of the present invention is that a direct memory access controller transfers data from the receive FIFO to memory during a reception, and from memory to a transmit FIFO during transmission.
Another aspect of the present invention is that a dual buffer ring structure manages the transmit and receive traffic.
Another aspect of the present invention is that a link list structure could be used to chain frames between repeaters of different transmission rates on different backplanes.
Another aspect of the present invention is that a buffer area is disposed between the two rings in memory to prevent packet fragmentation so that an arriving packet that does not fit within the space allotted between the buffer start address and the ring stop boundary is written past the ring stop boundary until the data buffer is complete and the start of the next frame will be wrapped to the ring""s start address.
Still another aspect of the present invention is that the repeater includes bridging means having a receiving and forwarding state, the receiving state for receiving signals from remote media access control managers and the forwarding state for responding to remote media access control managers.
These and various other advantages and features of novelty which characterize the invention are pointed out with particularity in the claims annexed hereto and form a part hereof. However, for a better understanding of the invention, its advantages, and the objects obtained by its use, reference should be made to the drawings which form a further part hereof, and to accompanying descriptive matter, in which there is illustrated and described specific examples of an apparatus in accordance with the invention.